This invention relates to hydraulic controls and more particularly to hydraulic controls for controlling the flow of fluid to and from a hydraulic retarder.
In prior art retarder control mechanisms, valving is utilized to direct fluid to the retarder when vehicle retardation is desired. During normal driving operation, the valving prevents fluid from entering the retarder. However, some residual fluid can remain in the retarder and the retarder otherwise is filled with air. The air and residual fluid in the retarder create parasitic losses in the transmission during normal vehicle operation. The parasitic losses reduce the overall efficiency of the transmission and result in the reduction of output power and a reduction in fuel economy.